Thermodynamic stability of Na2ZrO3 using the solid electrolyte galvanic cell technique

The sodium potential in the test electrode (a) Pt,O₂,Na₂ZrO₃,ZrO₂ was measured by using the emf technique employing Na-β^″-alumina as the solid electrolyte in conjunction with (b) Pt,O₂,Al₂O₃,NaAl₁₁O₁₇, (c) Pt,O₂,Na₂MoO₄,Na₂Mo₂O₇ and (d) Pt,Na₂CO₃,CO₂,O₂ as the reference electrodes over the ranges 880–1045, 700–800 and 850–940 K, respectively. The emf results between electrodes (b) and (c) were utilized for internal consistency checks. From the results on cells formed between (a) and (b) and those on (a) and (c), the standard Gibbs energy of formation, Δ_fG^o (kJ/mol) of Na₂ZrO₃ was determined to be −1699.4+0.3652T (K) valid over the temperature range 700–1045 K. The break in the emf data at 1045 K was corroborated by independent TG/DTA measurements carried out on Na₂ZrO₃ which exhibited an endotherm at 1055 K indicative of a phase transition in Na₂ZrO₃.     

Effect of silver on the formation of Bi2Sr2Ca2Cu3O10 (Bi-2 2 2 3) superconductors by sol–gel process

Bi-2 2 2 3 superconductors with silver additions are synthesized by sol–gel process. The effect of silver on the formation of Bi-2 2 2 3 phase is studied. The addition of silver brings down the reaction temperature as well as annealing time for the formation of Bi-2 2 2 3 phase. The presence of silver affects the Tc of the Bi-2 2 1 2 phase. The heat treatment of silver added Bi-2 2 2 3 samples above 1113 K show poor superconducting properties due to partial melting of Bi-2 2 2 3 phase. © 1998 Chapman & Hall     

Recent estimates of energy efficiency potential in the USA

Understanding the potential for reducing energy demand through increased end-use energy efficiency can inform energy and climate policy decisions. However, if potential estimates are vastly different, they engender controversial debates, clouding the usefulness of energy efficiency in shaping a clean energy future. A substantive question thus arises: is there a general consensus on the potential estimates? To answer this question, this paper reviews recent studies of US national and regional energy efficiency potential in buildings and industry. Although these studies are based on differing assumptions, methods, and data, they suggest technically possible reductions of ~25–40 % in electricity demand and ~30 % in natural gas demand in 2020 and economic reductions of ~10–25 % in electricity demand and ~20 % in natural gas demand in 2020. These estimates imply that electricity growth from 2009 to 2020 ranges from turning US electricity demand growth negative, to reducing it to a growth rate of ~0.3 %/year (compared to ~1 % baseline growth).     

Stimulus specificity of matrix metalloproteinase dependence of human T cell migration through a model basement membrane

Chemotaxis of human T lymphoblastoma cells of the Tsup-1 line, which migrate similarly to blood T cells, through a layer of basement membrane-like Matrigel on a polycarbonate micropore filter was evoked by vasoactive intestinal peptide (VIP; concentration for a maximal response, 10(-7)M), IL-2 (10(-9)M), and the chemokines RANTES (10(-10)M) and macrophage inflammatory protein-1 alpha (10(-10)M). Chemotactic concentrations of each factor increased Tsup-1 cell secretion of matrix metalloproteinase-9 (MMP-9), with significant responses by 4 h for VIP, IL-2, and IL-4, but only after 24 h for macrophage inflammatory protein-1 alpha and RANTES, as quantified by Western blots and zymography. 3H-Labeled type IV human collagen incorporated in the Matrigel layer was degraded by migrating Tsup-1 cells, as assessed by release of radioactive fragments of the collagen. The in situ degradation of type IV collagen in Matrigel by migrating Tsup-1 cells was enhanced most significantly by VIP, IL-2, and IL-4 after 4 h at concentrations that increased the secretion of MMP-9 optimally, but only after 24 h by macrophage inflammatory protein-1 alpha and RANTES. The specific MMP inhibitor GM6001 suppressed Tsup-1 cell MMP activity evoked by all stimuli, as determined by zymography and in situ degradation of 3H-Labeled type IV human collagen. The chemotactic migration of Tsup-1 cells through Matrigel, but not through a filter alone, in response to optimal concentrations of VIP, IL-2, and IL-4, but not the chemokines, was inhibited by GM6001, with a concentration dependence similar to that for suppression of MMP activity. Thus elicitation of T cell chemotactic migration through a model basement membrane by stimuli that increase MMP activity early in the response depends on degradation of matrix proteins by MMP, whereas stimuli that recruit MMP late may rely on early activation of other proteases.     

Heat-Mass Transfer and Friction Characteristics of Profiled Pins at Low Reynolds Numbers in Minichannels

Three pin fin array geometries (T60, T90, and T120) are investigated at low Reynolds numbers, Re _D  < 350, in a channel. The number in T60, T90, and T120 denotes the angle made by the pin surface with the end wall. Results show that the T120 pin is the most effective in facilitating momentum transport along the height of the pin and mitigates the undesired effect of low momentum and recirculating wakes. Additionally, pin T120 causes localized flow acceleration between pins near the end wall, which results in high heat transfer coefficients at the end wall. Overall, T120 has the highest heat transfer (augmentation ratio 2.9 at Re _D  = 325), without any increase in friction factor (augmentation ratio 8.3 at Re _D  = 325) from the baseline configuration of T90. However, T120 results in a large reduction in end-wall surface area, which reduces overall conductance, and in this respect T60 is superior in the range Re _D  < 150. A performance study of conductance under the constraint of the same pumping power in an equivalent plane channel shows that the profiled geometries T60 and T120 augment conductance between 40% and 250% over an equivalent channel.     

Gibbs’ energy of formation of YBa2Cu3O7-x (tetragonal)

The high temperature ceramic oxide superconductor YBa₂Cu₃O_7-x (1–2–3 compound) is generally synthesized in an oxygen-rich environment. Hence any method for determining its thermodynamic stability should operate at a high oxygen partial pressure. A solid-state cell incorporating CaF₂ as the electrolyte and functioning under pure oxygen at a pressure of 1·01 × 10⁵ Pa has been employed for the determination of the Gibbs’ energy of formation of the 1–2–3 compound. The configuration of the galvanic cell can be represented by: Pt, O₂, YBa₂Cu₃O_7−x , Y₂BaCuO₅, CuO, BaF₂/CaF₂/BaF₂, BaZrO₃, ZrO₂, O₂, Pt. Using the values of the standard Gibbs’ energy of formation of the compounds BaZrO₃ and Y₂BaCuO₅ from the literature, the Gibbs’ energy of formation of the 1–2–3 compound from the constituent binary oxides has been computed at different temperatures. The value ofx at each temperature is determined by the oxygen partial pressure. At 1023 K for O content of 6·5 the Gibbs’ energy of formation of the 1–2–3 compound is −261·7 kJ mol⁻¹.     

Standard Gibbs energy of formation of Mo3Te4 by emf measurements

The emf of the galvanic cells Pt, Mo, MoO₂¦8 YSZ¦‘FeO’, Fe, Pt (I) and Pt, Fe,‘FeO’ ¦8 YSZ¦MoO₂, Mo₃Te₄, MoTe₂(), C, Pt (II) were measured over the temperature ranges 837 to 1151 K and 775 to 1196 K, respectively, using 8 mass% yttria-stabilized zirconia (8 YSZ) as the solid electrolyte. From the emf values, the partial molar Gibbs energy of solution of molybdenum in Mo₃Te₄/MoTe₂(), was found to be

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. Using the literature data for the Gibbs energy of formation of MoTe₂(). the expression ΔG°_f(Mo₃Te_4,s) ± 5.97 (kj/mol) = −253.58 + 0.09214T(K) was derived for the range 775 to 1196 K. A third-law analysis yielded a value of −209 ± 10 kJ/mol for ΔH°_f.298^o of Mo₃Te₄(s).     

Highly Ordered Good Crystalline ZnO-Doped WO3 Thin Films Suitable for Optoelectronic Applications

Highly ordered ZnO-doped WO₃ thin films with good crystalline quality are prepared using radio frequency magnetron sputtering technique, and its morphological and structural properties are studied using various characterization tools such as field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction technique, micro-Raman spectroscopy, and x-ray photoelectron spectroscopy. Morphological analysis shows a smooth surface for pure film, whereas the ZnO-doped films presents a dense distribution of grains of larger sizes with well-defined grain boundary. X-ray diffraction studies reveal the enhancement of crystalline quality of the films with increase in ZnO doping concentration up to 5 wt.%, beyond which the crystalline quality gets deteriorated. A phase modification from a single monoclinic WO₃ phase to mixed monoclinic WO₃ and W₁₈O₄₉ phases is observed for films with higher ZnO doping concentrations.

     

Development of an Alternate Route for the Hydrolysis of Cassava Flour

Moldy wheat bran as such is used as a source of amyloglucosidase enzyme (EC 3.2.1.3) in the hydrolysis of cassava flour. 92–94% of glucose was obtained in the hydrolysate after 16 h of hydrolysis. The process was found to be economical compared to the hydrolysis using commercially available liquid enzymes.